* When I see my flight plan, I understand why it's curved.

* When I see clouds that a radar says should be a certain distance away, I understand what makes me able to see them.

* Where weather is moving, how it's moving, and why certain weather patterns even exist at all.

* When I see a landmass on water I can accurately guess how far away it is, and I can understand why moving even a small amount upwards lets me see so much more (and why it was such an advantage on ships to have a vantage point only 20 to 30 feet up in the air).

* How stars move in the night sky is predictable.

* Why the "north" star exists and is accurate as a directional indicator.

* Where constellations are, and how they're different depending on what latitude I'm currently observing the night sky from.

* The fact that tides exist, and how they work.

* I understand how and what satellites are, when I can see them, and I can predict when I'm going to lose signal from them given certain circumstances.

* Every other planet I've observed is round. The moon is round. The sun is round.

None of this works if Earth isn't round, and that's just off the top of my head. The point here is that so many things stop making sense if you don't accept the fact that the Earth is round, and so you're constantly failing to predict or understand a whole host of problems that, yes, do come up in my daily life.

This isn't about "happening to pick the right set of beliefs", it's about matching what you're told with what you're observing and noting a singular and profound consistency across disciplines, uniformly converging on one single, basic fact; the Earth is round.

1) Flight plans only look curved because you are using a map projection that assumes a spherical globe. If you use the right flat earth map you will find that flight paths follow straight lines.

2) Clouds and distances still exist in a flat earth and the clouds float above the earth. This is why they are detectable by radar.

3) Weather patterns exist on the flat earth because the sun moves across it and heats it unevenly.

4) An ant on a perfectly flat desk can also see much more from an elevated vantage point. Are you claiming desks are also spherical?

5) No one is claiming the stars nor the flat earth is stationary. Both can rotate around various axes and the resulting movement can be predicted.

6) The north star sits slightly above the plane of the flat earth and far to the north so that it appears north from any vantage point on the earth. This is just because of its distance.

7) The constellations differ depending on latitude because of the refraction of the atmosphere. This bends the light rays.

8) Tides are caused by the pull of the moon as it traverses above the flat earth and attracts the water in the ocean.

9) The other planets are also flat and only appear round because they are tidally locked with respect to the earth.

However, there is no predictive value in any of what you've written here, so while they may be, to some, "refutations", they are not in any way useful.

If there were actually any flat earthers who cared about reason, because of the lack of predictive value (not to mention the contradictory/unprovable nature of what you've written here), they would not remain flat earthers for very long.

I -believe- the earth is round. But the intellectual honesty I’ve taken from The flat earthers tells me I have delegated my source of truth on that topic to others whom I am trusting to relay the truth. Maybe one day I’ll get into orbit and see for myself. With my own eyes. But that is beside the point of what I learned from them. I learned any time I outsource what I think is true to third parties, there is a risk of me believing a lie. Because people lie sometimes. And sometimes they draw conclusions based on assumptions and conjecture. My thought process is non-binary or more honestly, tri-state. I have true, false, and I have not observed that to be either true or false.

1. I regularly do video conferences with friends and colleagues on other continents; I can see if its light or dark in their windows. I have personally verified that some of my friends and colleagues and their places exist.

2. I have seen many ships disappear behind the horizon, and I have seen mountains disappear behind the horizon from ships; I have verified the accuracy of Vesselfinder (by comparing transits through lines in Vesselfinder with what I can see) and checked that it is at the expected distance. (I was curious about the delay.)

3. I have watched the ISS (once even trailed by the ATV) and it was right where HeavensAbove said it would be. And 90 minutes later I did it again. I have personally verified the basic math behind circular orbits.

4. I have experienced changing radio band propagation conditions consistent with a day/night cycle that is different in different places. Such as grayline DX, which is good propagation along the day/night line. Which implies the day/night line is real. And based on the reports I received I know it matches the map. I have built some transmitters and receivers myself.

5. I have flown between continents, been jetlagged and changed my clock's time (or maybe changing my wristwatches time is changing the sun and causing the jetlag?). I have watched the entire flight through windows, so I know I traveled very far.

6. I have seen the motion behind Foucault's pendulum over enough time (I've been to the museum long enough to verify that the pendulum plane rotates as expected, and I saw nobody messing with it in any obvious way.) We also did the same experiment in school. In school, we did the math for the Coriolis force, and talked about how it comes up as a significant factor in unexpected places (e.g. railway). Someone would talk.

7. I've observed the direction of the toilet swirl, and whirlpools in lakes.

8. I've experienced tide levels and swum with/against tide currents (sometimes even in the same place). I have also seen the moon in the sky and I think if it would be inconsistent someone would've noticed by now.

9. I've seen the shape of day/light boundary on the moon. Now that's the moon, but that one's clearly spherical, which is one data point.

10. I had a trusted fried, but he's got a PhD in astrophysics now, so he must be in on it and we cannot be friends anymore. /s

And I'm just some nerd, I haven't done too many experiments. I'm sure I could still extend the list, but of course there's no point since neither of us believe in the flat earth "theory".

There's no intellectual honesty in coming up with fake experiments like flat earthers do (if they even go to the trouble).

Before 2020, I thought flat earth like conspiracies were harmless fun (and I still think that a significant number of flat earthers are just having fun), and maybe they are. But after spending several hundred hours "discussing" many conspiracy theories (people I know and care about started believing very outlandish ones, like chemtrails and 5G causing covid) the last two years, and first hand witnessing intellectual incompentence (complete math illiteracy down to calculating a percentage, complete rejection of the concept of mathematical proofs, zero concept of scale e.g. of organizations and communities, complete refusal to read original research, insisting on "reading between the lines" to interpret texts claims made in texts into the opposite) I have come to see conspiracy theories and fake or un-intellectuality (is that a word?) as very dangerous (the "can cause death" type of danger).

this is not an indication of a round earth. the coriolis effect on this is negligible.

1: There are time zones in the flat earth model. The earth is a flat disc with antarctica (or is it the north pole?) at the center, and the sun moves around it in a circle, so the places opposite the sun are in nighttime

2: Believe it or not, flat-earthers believe light only travels so far, which is why things disappear "over the horizon"

4: I don't actually understand this one, but I suspect they'd handwave and talk about the same point in (1)

5: Same as (1)

I don't think flat-earthers have accounted for Foucalt's pendulum however.

That does not match my experience. I did looked into it and I found no consistent model of a flat earth. Lots and lots of words and sometimes even with consistent logic at times - but build upon completely false assumptions and flawed logic and therefore worthless. (you can proof anything, if your basic assumptions are made up)

"I don't think flat-earthers have accounted for Foucalt's pendulum however. "

And some of them tried and believe they did, but only when ignoring other facts and used twisted logic.

Like some parent poster had said - it is not about proof, but way more about ideology.

Otherwise they could very easily have a real proof, by sending up a weatherballoon, or organise a boat trip to the end of the world. But since they always refuse to do so (I challenged quite some with that concept) or even really think about it - they likely suspect inside that they are wrong, but rather not confirm for real, because then they would have to abolish a lot of their other ideology like chemtrails etc.

1. Find a sufficiently large "shallow" body of water. 2. Build a number a number of masts/poles in a straight line, all with an identical height over the water.

Now when standing at the shore and looking at the masts I predicts one of two things.

a. you can see all masts in their entirety with a telescope, or b. you can see less and less of the masts the further away they are.

There are actual places with power lines that satisfy this requirement. For b. you can use high school math to reason about the curvature needed to explain the results. There is no such sound logic (to my knowledge) explaining this for a flat surface.

I haven't done the experiment, but this brings it back to trusting scientists (light bends just above the water, but doesn't 4m above the water). I would need to do additional experiments to understand the refraction.

The simplified method works by considering two cities along the same meridian and measuring both the distance between them and the difference in angles of the shadows cast by the sun on a vertical rod (a gnomon) in each city at noon on the summer solstice. The two cities used were Alexandria and Syene (modern Aswan), and the distance between the cities was measured by professional bematists.[16] A geometric calculation reveals that the circumference of the Earth is the distance between the two cities divided by the difference in shadow angles expressed as a fraction of one turn.

https://en.wikipedia.org/wiki/Eratosthenes#Measurement_of_Ea...

They found a road that was almost due north and south (US 183 from Bassett, NE to 370 miles south in Coldwater, KS). They measured the elevation of Antares at its zenith one night, then again the next. From that they get the change in latitude. Combined with odometer data and some estimates for wiggles, and end with a result about 5% larger than the best-known solution.

Their measuring instrument was a Ryder van dubbed "The Van of Eratosthenes."

As an aside, later in the same episode is when I learned about GPS. https://youtu.be/yRY2SkMTafc?t=2968 . "This is the future of mapping."

Not true. From any non-zero height above an infinite flat desk you can see the entire desk.

(A good response to this, of course, is to ask for a model for how much the light curves. A vague description is not a predictive, scientifically-testable model, unless it's a very wrong description.)

How do you you know that light travels in straight lines? Maybe it travels in curved lines!

You turn on a light source and look at how the light spreads. Light does not - besides a tiny bit of diffraction - bend into the shadow area behind obstacles.

In fact, that's how mirages form.

You obviously have to perform your experiments under control conditions, so pick a time and place with negligible variation in index of refraction of the atmosphere. Or measure and account for it.

I don't know that I am; you were the one to bring up the implicit “light travels in straight lines” assumption with your claim about ants on a flat table. Obviously if I think the earth is flat, I don't believe that.

> Light does not - besides a tiny bit of diffraction - bend into the shadow area behind obstacles.

It depends how much distance you give the light. Shadows are noticeably blurry if your hand is close to the light source.

> You obviously have to perform your experiments under control conditions, so pick a time and place with negligible variation in index of refraction of the atmosphere.

You're never going to get a situation where the air temperature is consistent enough for this; it varies by height (as does pressure). And, again, unless you can show me that “index of refraction” is a thing that applies to air, I'm not going to believe something as ludicrous as Snell's Law. (After all, isn't the speed of light a constant? The whole derivation rests on the assumption that it varies depending on the medium!)

I would argue that it was implied before I first commented. Without any assumption about the way light moves, you can not answer visibility questions on spheres and desks. The first comment talked about a spherical earth and certainly assumed light behaves as commonly accepted, the response did not question this either. Only after it has been pointed out that the response was not valid, the behavior of light entered the discussion.

It depends how much distance you give the light. Shadows are noticeably blurry if your hand is close to the light source.

Use a point light source or account for the size and shape of your light source.

You're never going to get a situation where the air temperature is consistent enough for this; it varies by height (as does pressure). And, again, unless you can show me that “index of refraction” is a thing that applies to air, I'm not going to believe something as ludicrous as Snell's Law. (After all, isn't the speed of light a constant? The whole derivation rests on the assumption that it varies depending on the medium!)

Make up your mind. Does light move in straight lines or doesn't it? Does a medium influence light traveling through it or doesn't it? If, how? You questioned light moving in straight line, it is beyond me why you would now also question light moving not in straight lines. Or is it just the mechanism that you are questioning? And nobody claims the speed of light is constant, the speed of light in vacuum is constant.

And in order to cut this cat and mouse game short, just present your complete theory of how the world works upfront. There is no point in such a discussion if you keep changing what you believe or say every time an issue is pointed out.

Yeah you can: light moves the way it actually moves in real life: the way you can see with your eyes.

> Make up your mind. Does light move in straight lines or doesn't it?

I was assuming what you said to be true, and showing that it wasn't sufficient to rule out what I was saying.

---

In reality, I understand how light behaves (not quite as simple as “straight lines”, but that's a good enough approximation to explain mirrors). I know that you do, too. You aren't demonstrating that, though; you're just name-dropping facts without showing why they have to be true, why that's the only way the universe can work because if it didn't work that way, observations could be made that cannot actually be made.

I have not got a complete model of “flat earth cosmology” to present you, because I believe such a thing doesn't exist. I did have a consistent, incomplete model in mind when I was writing those comments, though: one where light curves upwards in a manner that causes the surface of a plane to appear spherical. (However, objects on the horizon would be a different size to on a real sphere, which could be used to falsify my model by comparing it with real-world observation.) I wasn't moving the goalposts.

Much harder to argue for this these days now that amateur telescopes/decent camera optics have become reasonably cheap and cameras too. Jupiter has a rotation period of only ten hours, so one can easily see it rotate within one night. The sun takes a bit longer since it has a rotation period of 25-38d (depends on the latitude which is quite interesting) and if there are no sun spots it's kind of hard to tell.

For example to make 10 different flight paths over the pole make sense on flat earth you need 10 different flat earth maps contradicting each other. The only way to make all the flight paths make sense is round Earth.

Same with weather, day-night and seasons - you can get some of them with different flat earth models, but these models contradict each other. To get all the daily and yearly patterns at the same time you need round Earth.

As for tides I'd like to see even one good flat earth model where moon is visible in the correct place on the sky at the same time looking from equator, north hemisphere and south hemisphere. Most flat earth models put moon 180 degree away from "center of flat earth" opposite of the sun, which is obviously wrong (cause you can see moon and sun at once in many places).

And there's such problems with each point. But that's not a problem, because flatearthers don't want to have a consistent model of reality, they just want to think The System is out there trying to deceive them. So it's fine having 100 different contradicting models that explain one thing each.

A flat shape is impossible because the gravitational field would be vastly different on a planar body than on a spherical one, as I go further from the center of mass the further I go towards the edge.

And how gravity works can easily be demonstrated in a lab setting.

[1] https://www.britannica.com/science/gravity-physics/Accelerat...

Day length in Melbourne, Australia today is 14 hours, 25 minutes. The sun just set half an hour ago.

If you know someone who lives in those places, you can call them for confirmation (unless they're part of the conspiracy).

How do you explain the observations with flat earth?

Just came off the plane yesterday. I remember the earth on the flight map was perfectly flat. The path was weirdly curved though...

EDIT: Wait, didn't get the sarcasm, my bad. :P

Flat-earthers should be suing airlines for flying them further than needed. Make them put their money where their mouth is.

https://www.khanacademy.org/humanities/big-history-project/s...

For those who don't know it, in brief: Put a vertical pole in flat ground at noon and measure the length of the shadow. The next day, drive an hour or two directly north or south and do the same measurement at noon again. With a bit of trigonometry, you can estimate the earth's circumference - or for our purposes, at least prove to yourself that the earth is not flat, as the shadows will be different lengths with the sun in nearly the same position both times.

Of course, there is a separate discussion about whether we should consider light trigonometry within the bounds of what modern laymen should be expected to handle.

As the article also states, the ancients observed that as ships passed below the horizon, the hulls disappeared before the masts - this is also within reach of most laymen.

Sure, but a flat earther will just argue that the sun is much closer than scientists claim, which explains the difference in shadow length. And again, what's a layman to do?

The best experiment to prove the earth is round that I've thought up involves the Coriolis Effect and a rifle fired at different points both north and south of the equator. Unfortunately that requires international travel with firearms, making it legally difficult to try.

It is interesting that is not uncommon for flat earthers to be more "scientific" that many spherical earthers in recognizing that many spherical Earth arguments are not sufficient by themselves. Of course the spherical earthers happen to be right, while the flat earthers then proceed to invent completely implausible theories to support their beliefs, but they deserve some recognition for the first stage.

Sure, there’s no critical thinking for a lot of it, in the same way that I don’t think critically about all the physics and engineering before I step on an airplane. The entire point of living in a society is that you don’t have to do everything yourself — you can outsource a lot of that critical thinking to other people who (are paid to) care more than you. You can just go with the flow and actually have a pretty good track record for believing the right things.

[1] https://en.wikipedia.org/wiki/Geostationary_Operational_Envi...

The question is how you distinguish the two: always go mainstream? Always counter the old-fashioned ways? Trust the best credentialed person? Distrust credentials achieved during brainwashing, go with independent self-taught thinkers? Independently verify every claim, replicating experiments from first principles?

The only way you could really prove it is to define a set of axioms that you some how convince them to agree to. And then get them to agree to logic. And then construct an experiment using those rules whereby if the Earth is round then they die. And see if they are willing to test it. And if they don’t then you win. And if they do it and die then you also win.

Salar de Uyuni - "As a result, the variation in the surface elevation over the 10,582-square-kilometer (4,086 sq mi) area of Salar de Uyuni is less than 1 meter (3 ft 3 in) normal to the Earth's circumference".

That's less than 1 in 6371000 - pretty smooth, no?

> That's too prone to terrain irregularities

Nah, it's still doable, especially on that^ salt flat - if you have two close holes and a 3rd one 55km away, a flat earth will let you line up the laser through all three with less than 2m of adjustment. By my rough calculations, on a spherical earth, the laser will be ~250m above ground at 55km - pretty obviously proving the hypothesis incorrect, no?

It's not really that hard to estimate the circumference of the earth and prove that it has to be spherical. But most methods I know of require quite a bit of driving, or friends that are far away and can take a measurement at exactly the same time.

I'm not a flat earther but I do want to do my own measurement of the earth's circumference one day for fun.

To be precise, the earth is not spherical. It's unfortunately not even an ellipsoid: I live well above the sea level yet my home is like 20 meters below the surface of the WGS84 reference ellipsoid.

The simplest way I could come up with while discussing the issue with my kids, was to call a grandma on the other side of the globe and ask here when did she have a sunset. It still could mean that the earth is a hemisphere, but at least it's not pancake-style flat.

However, to move forward in life, we must accept certain axioms so that we can be effective and productive. (Prove food is nutritious, prove I won't die in the next 5 minutes, prove my parents are benevolent actors, prove my children are actually mine). At some point, you can litigate anything you want, and the real decision is, what hills are you willing to die on. For me, that's determined strongly by impact to my life, and also partly by interest.

What I'm saying is, don't argue that the flat earthers are wrong. Argue that they are useless because what they are arguing about doesn't matter.

I mean, I guess they could, but they'd clearly be bending over backwards to make a logical fallacy.

Maybe not for you :)

In my example the number need not be directly overhead either. It could be drawn in the middle of a very long room where you and the other person are at opposite ends. You're both looking at it at an angle and both still seeing different numbers, although in a very skewed perspective - I don't know how flat earthers account for perspective and projection in their skydome or whatever.

The Orion-is-upside-down-here thing was the first time I noticed something that drove it home to me that we live on a sphere.